The present invention relates to a scroll saw machine having a sawing blade which is moved upwardly and downwardly by a motor to cut a workpiece along a desired curve. In addition, the present invention relates to a scroll saw machine whose sawing blade is tightly set in a vertical position through a table and moved up and down by a motor as a workpiece on the table is moved to be cut along a desired curve by the blade. The invention more particularly relates to a scroll saw machine lo whose sawing blade always can be set at an appropriate tension depending on the strength of the blade and/or can be easily attached so as to orient the width of the blade either forwardly or sidewardly.
Since the compressive strength of the sawing blade of a scroll saw is very low, a first end of the blade is coupled to the lower end of a piston, which is moved upwardly and downwardly by a motor. The blade is supported at a second end thereof by a U-shaped arm, provided so as not to interfere with a workpiece, and the blade is pulled downwardly at the second end. Thus, the blade is reciprocated by upward and downward movement of the piston while always keeping the blade taut.
Conventional scroll saws have been provided previously which are of the heavy, fixed-installation type, as disclosed in Japanese Patent Examined Publications Nos. 3158/77 and 20720/78. A workpiece is cut along a desired curve by the conventional scroll saw, while the workpiece, positioned on a table, is turned relative to a sawing blade.
In a hand-held scroll saw, no table is provided, and a workpiece is not turned relative to a sawing blade. Instead, the workpiece is fixed in position. Hence, the hand-held scroll saw requires not only a U-shaped arm thereof to be compact, but also a blade support device for reciprocating the blade while keeping the blade taut. In the hand-held scroll saw, the construction of the blade support device is paramount over making the U-shaped arm compact.
Thus, the blade support device of the hand-held scroll saw typically cannot be constituted similarly to the scroll saws of the heavy, fixed-installation type, or manufactured by making the blade support device compact by using components equivalent to the scroll saws of the heavy, fixed-installation type. Additionally, since the range of the workpiece cut off by the hand-held scroll saw would be made narrow if the U-shaped arm thereof is made compact, the range must be prevented from being made narrow by making the U-shaped arm large and cumbersome. Thus, in conventional hand-held saws, a compact hand-held scroll saw with a suitable range cannot be achieved. This presents a problem.
Further, in a conventional scroll saw machine of the fixed-installation type, a sawing blade is coupled at the lower end thereof to a piston, which is moved upwardly and downwardly by a motor, and the blade is always pulled upwardly at the upper end thereof as the blade is moved upwardly and downwardly. The conventional scroll saw machine of the fixed-installation type comprises a body including a table which is the upper part of the body, which bears a workpiece thereon and which has a slit through which the sawing blade extends, a piston which is provided under the slit and to which the blade is secured at the upper end thereof, and a piston drive means having a motor in an appropriate position to drive the piston; an arm secured lo at the lower portion thereof to the body and extending so that the arm rises from a prescribed point behind the table and the front end of the upper portion of the arm is located at a prescribed point over the piston; and a suspension unit which is attached to the arm at the front end of the upper portion thereof and to which the blade, which is coupled at the lower end thereof to the upper end of the piston, is secured at the upper end of the blade, as disclosed in Japanese Patent Examined Publications Nos. 3158/77, 20720/78 and 49361/82.
The suspension unit for supporting the sawing blade at the upper end thereof and for tightening the blade in the vertical movement of the piston is not capable of adjusting the blade tension. Thus, there are problems that if a buckling load acts on a sawing blade having a very low buckling strength because of the resistance of the workpiece to the blade in the upward movement of the piston, the blade is likely to break and the cutting precision of the workpiece by the blade is low.
Other problems include that the suspension unit has a complicated structure and projects substantially over the front end of the upper portion of the arm, resulting in the height of the machine being large. Since the sawing blade cannot be attached so as to orient the width thereof sidewardly (although it can be attached so as to orient the width thereof forwardly), there is yet another problem that the maximum length of the workpiece able to cut is not larger than the distance between the blade and the arm.